In the prior art, peak data rates of a cell have been significantly improved, but rates at the edge of the cell remain far below the peak rates, and in view of this, extensive investigation has been made on improving the throughput of a User Equipment (UE), and the average throughput, at the edge of the cell, where dynamical three-dimension (3D) beam-forming is a key technology to improve the average throughput at the edge of the cell.
Corresponding channel state information needs to be fed back in order to support transmission of dynamical 3D beam-forming. For example, a Channel Quality Indicator (CQI) is configured for UE scheduling, a Modulation and Coding Scheme (MCS) and/or Multiple-User Multiple Input Multiple Output (MIMO) pairing, etc., a Pre-coding Matrix Indicator (PMI) is configured for determining beam-forming, multiple-user scheduling, MU-MIMO pairing, etc., and Rank Indication (RI) information can be configured for determining the number of layers used for data transmission, etc.
In the existing Long Term Evolution/Long Term Evolution-Advanced (LTE/LTE-A) system, there are supported five types of non-periodical channel state information feedback, i.e., Physical Uplink Shared Channel (PUSCH) feedback modes, and four types of periodical channel state information feedbacks, i.e., Physical Uplink Control Channel (PUCCH) feedback modes, respectively as depicted in Table 1 and Table 2, where the mode 1-2 in Table 1 is configured to feed back an RI, a sub-band PMI and a broadband CQI, the mode 2-2 is configured to feed back an RI, a broadband CQI/PMI, and a UE selected sub-band CQI/PMI, the mode 2-0 supports a feedback of an RI, a broadband CQI, and a UE selected sub-band CQI, the mode 3-0 is configured to report an RI, a broadband CQI, and a sub-band CQI, and the mode 3-1 is configured to report an RI, a broadband CQI/PMI, and a sub-band CQI; and the mode 1-0 in Table 2 is configured to feed back a broadband CQI, the mode 1-1 includes two sub-modes supporting a feedback of an RI, a broadband PMI and a CQI, the mode 2-0 is configured to feed back a UE selected sub-band CQI, and a broadband CQI, and the mode 2-1 is configured to feed back RI, broadband PMI/CQI and sub-band CQI (or sub-band PMI) information.
TABLE 1CQI and PMI feedback types of PUSCH report modesPMI feedback typeNo PMISingle PMIMulti-PMIPUSCH CQIBroadbandMode 1-2feedback type(broadband CQI)UE selectedMode 2-0Mode 2-2(sub-band CQI)Higher-layerMode 3-0Mode 3-1configured(sub-band CQI)
TABLE 2CQI and PMI feedback types of PUCCH report modesPMI feedback typeNo PMISingle PMIPUCCH CQIBroadbandMode 1-0Mode 1-1Feedback type(broadband CQI)UE selectedMode 2-0Mode 2-1(sub-band CQI)
Dynamical 3D beam-forming involves both horizontal and vertical beam-forming to thereby improve the signal to noise ratio of a target UE. A transmitter has to know a pre-coding matrix of the target UE in the horizontal and vertical dimension to thereby perform beam-forming on the UE, that is, the target UE has to feed back horizontal and vertical PMIs, but an existing feedback solution supports only a feedback of the horizontal PMIs but no 3D beam-forming.
In summary, the vertical PMIs can not be fed back in the prior art so that dynamical 3D beam-forming may be impossible.